[css-syntax-3] Fix the loop *properly*, to not change top-level behavior of '@foo;;foo{}'.

Author: tabatkins

css-syntax-3/Overview.bs

@@ -2558,7 +2558,8 @@ Consume a qualified rule</h4>
 
 	To <dfn>consume a qualified rule</dfn>,
 	from a [=token stream=] |input|,
-	given an optional bool |nested| (default false):
+	given an optional [=token=] |stop token|
+	and an optional bool |nested| (default false):
 
 	Let |rule| be a new [=qualified rule=]
 	with its prelude, declarations, and child rules
@@ -2568,10 +2569,9 @@ Consume a qualified rule</h4>
 
 	<dl>
 		<dt><<EOF-token>>
-		<dt><<semicolon-token>>
+		<dt>|stop token| (if passed)
 		<dd>
 			This is a <a>parse error</a>.
-			[=Discard a token=] from |input|.
 			Return nothing.
 
 		<dt><a href="#tokendef-close-curly">&lt;}-token></a>
@@ -2713,7 +2713,8 @@ Consume a block's contents</h4>
 
 			Otherwise, [=restore a mark=] from |input|,
 			then [=consume a qualified rule=] from |input|,
-			with |nested| set to true.
+			with |nested| set to true,
+			and <<semicolon-token>> as the |stop token|.
 			If a [=rule=] was returned,
 			append it to |rules|.
 	</dl>